Protected and insulated heat treatment coil



Jan. 7, 1941. H. E, SOMES 2,227,866

PROTECTED AND INSULATED HEAT TREATMENT COIL Filed June 29, 1958 PatentedJan.' 7, 1941 UNITED STATES PATENT OFFICE V2.22am

raoTEcTEn AND rNsmTEn HEAT TREATMENT n.

Howard E. Sonics, Detroit, Mich. Application Jnne 29, 1938, Serial No.216,614

2Claims.

The present invention relates to heat treatment coils for heatingarticles by means of high frequency electromagnetic induction currents.

More specifically, it relates to a readily inter- 5 changeable coil forcarrying high intensity, high frequency currents, preferably mountedupon a laminated core of magnetic material, for insertion into articleswhich are to be heated by induction. Such coil is of the general typedisclosed in my copending case Serial No. 101,993, filed September 22,1936.

An object of the present invention is to provide a coil of this naturewith efficient insulation and also to provide it with an armor or otherexternal protection made of highly refractory material, which willprevent mechanical injury to the coil.

A further object is to provide an armor for such coils which while madeof metal will be substantially free from eddy currents, this resultbeing attained by breaking up the armor into small component parts whichare not in electrical contact with one another and which do not formclosed circuits.

Still more specifically, the invention relates to a heat treating coilconsisting of a mandrel having radially arranged laminations mountedthereon with a heat treating coil made of hollow f conductive tubingsurrounding said laminations, the coil being insulated from theremaining parts, an armor consisting of a number of narrow resilientsplit rings of highly refractory metal, such as Chromel A, beingprovided overthe coil to protect the same from mechanical injury.

One embodiment of the device is illustrated in the accompanying drawingwherein: i

Figure 1 is an elevation, partly in longitudinal axial section, of acoil together with the mounting means for the same, and

Figure 2 is a cross section on the line 2-2 of the structure shown inFigure 1.

For convenience of manipulation the coil and its laminations are mountedon a hollow mandrel I having the bore 8. This mandrel has a portion ofincreased diameter near one end thereof and` this portion is preferablyundercut as shown at i8 to provide an annular retaining hook or groove.

A series of laminations 2 is arranged annularly about this end of themandrel I, each lamination being preferably tapered in a radialdirection, that is, in such manner that the opposite faces of eachlamination would converge toward the center of the mandrel, if extended.To hold the laminations on the mandrel a retaining ring 3 is 55 providedwhich ts over the mandrel and which (Cl. 21S-13) has a projectingportion I9 forming an' annular hook directed oppositely to the hook I8.

The laminations are, of course, correspondingly shaped so that the hooksI8 and I9 will hold them in position firmly and securelyr` when they 5are engaged with such laminations. A key 1 of any suitable nature may beengaged against the outside of the ring 3 to hold it in position and thekey 1 will itself be engaged in a suitable slot in the mandrel I, sothat once the ring 3 is in its proper position to hold the laminationsand the key 1 is engaged in its groove in the mandrel the laminationswill be prevented from becoming loosened. The key 1 may be split ordivided ring seated in an annular groove 3i, for example, and the partsof this ring may be held in place by means of a resilient ring 9 engagedtherearound.

The laminations 2 have at one end an angularly offset portion I0,preferably projecting at right angles as shown in Figure 1, which servesas an abutment for the outer end of the winding 2|. 'I'his windingconsists of a suitable number of turns of tubing made of conductivematerial, preferably copper tubing which will serve to conductelectricity and also provide a conduit for a cooling liquid.

This coil is preferably wound on a form and slipped on the core, with aring of mica or similar refractory insulating material I3, interposedbetween it and the outer edges of the laminations. The individual turnsof the Winding may also be insulated from one another by split rings I4of similar insulating material, which may be threaded into the saidspaces, or insulation of any other type may be introduced in anyfeasible manner 3- between the turns. In certain cases a mere spacing ofthe turns from one another by air spaces will suffice, particularly ifthe coil is rigid enough to maintain its turns properly spaced from oneanother.

A cooperating set of radial laminations II is arranged to abut againstthe remaining end of the coil, these laminations being retained in thehead or collar 4 and secured to one another by a suitable binding I2 ofwire or cord, which serves merely to perform a mechanical retainingfunction.

The laminations II have a shoulder as shown at 22 and a ring 23 bearsagainst this shoulder and is secured to the head 4 by means of bolts!mounted in suitable openings 6 in the ring 23 and entering screwthreaded bores I1 in the head or collar 4.

'I'his collar 4 may be in turn secured to th mandrel I by any suitablemeans, for example by means of a nut 24 threadedon the said mandrel.

The copper or other tubing may be insulated vfrom its surroundingconducting parts by any suitable means, for example, byporcelain-enameling, by oxidizing the conductor to provide a film ofoxide, or by other known ways of providing insulation, and a layer ofmica 20 is preferably placed around the coil 2| as shown. Othermaterials may also be used for this purpose, but mica Will ordinarily bethe preferred form of insulation employed.

In order to provide a suitable armor for the winding, use is made ofresilient rings made of a high resistance non-magnetic or substantiallynon-magnetic material, such as Chromel A, which is formed into thinnarrow split rings as shown at I5, each suchring having a gap therein,as indicated at i6, for the double purpose of increasing the range ofresiliency of the ring and of preventing it from forming a closed turnin which eddy currents could flow. The gaps in the rings willpreferably, of course, be located at distributed points about theperiphery of the coil, so that they will not all come in the same lineor nearly in the same line with one another. Preferably also, theserings will have an insulating coating, such as an oxide lm, so as toavoid short circuiting one another if they should accidentally beshifted into contact with one another, or they may lie positively heldin spaced relation axially by interposed insulating material. Forexample, they may be axially spaced by means of a glass threadimpregnated with one of the porcelain enamel compounds or with glyptaland baked. K

A suitable connection will be made to each end of the coil 2| to feedthe electrical energy and the cooling liquid through the same. One lead25 for this purpose will preferably run through the collar 4, while theother lead 26 is grounded and connects to the bore 8. Connection to suchleads may be made in any desired manner, for example, by welding or bythreaded or other fittings. Insulation 29 surrounding the lead 25 willserve to insulate it from the collar 4 and other parts through which itpasses. This lead constitutes the upper end of the coil 2|.

The cooling liquid enters through the inlet tube 25 and after traversingthe coil 2| will be discharged through the grounded outlet tube 26 whichis connected to the last turn. This tube 26 leads the Water to thecentral bore 28 which is located at one end of the mandrel I. Since themandrel is intended to be used mostly in a vertical position with thecollar 4 upward, it is obvious that the water will discharge bygravitation from the passage 28. If the coil is to be used in a. hori-Zontal position it will be preferable to provide a plug In to shut oiIthe bore I, as shown, so as w prevent the water from traveling in thewrong direction through the bore I.

In operation the coil is introduced into the bore of the article whichis to be heat treated, so that the high frequency flux produced by thecoil 2| in the laminations 2 and will now in the inner surface portionsof the article being heat treated, said flux entering and leaving thelaminations at the portions I and 21.' This high frequency magnetic fluxwill thereupon produce the necessary heat in the article as disclosed incopending case Serial No. 101,993, iiled September 22,1936.

The armor I which, for example, in one speciilc instance was made ofChromel rings having a thickness oi' fifteen one thousandths of one inchand a. width of six one hundredths ot one inch. occupies a relativelysmall space, has a high electrical resistance and is non-magnetic sothat very little loss due to eddy currents and/or hysteresis is producedin said rings. particularly inasmuch as each ring is split. However,these rings are very strong and highly refractory and serve to protectthe winding beneath them from short circuits which might otherwise occurdue to abrasion or accidental presence of metal turnings or borings inthe article being treated. as well as against any dropping of fusedmetal upon the winding.

The coil and its mounting means are so designed that it is possible tomanufacture them in quantity without dimculty and the construction ismuch simplified by the fact that the coils are form-wound.

I claim:

1. A heating coil assembly comprising a support, a core made oflaminations of magnetic material mounted thereon, a form-wound coilsurrounding the core, means for insulating the coil from the core, anumber of split rings made of metallic non-magnetic material surroundingthe coil in staggered relation, and insulation between the coil and therings.

2. A heating coil assembly comprising a support, a core made oflaminations of magnetic material mounted thereon, a form-wound coilconsisting of tubing and providing a passage for a cooling fluid,surrounding the core, refractory insulation comprising glass thread anda. refractory binder separating the coil from the core, furtherrefractory insulation surrounding the coil and a number of spaceddiscontinuous staggered rings made of refractory metallic nonmagnetichigh resistance resilient material enclosing said last-named insulationand resillently holding it to the coil.

HOWARD E. SOMES.

